(University of Illinois at Urbana-Champaign) Rats exposed in the womb and during lactation to plasticizing chemicals known as phthalates had fewer neurons and synapses than those that were not exposed, researchers report in a new study. The phthalate-exposed rats had reductions in the size of their medial prefrontal cortex, a brain region that regulates behavior, and showed deficits in cognitive flexibility. The variety of phthalates and quantities used in the study were environmentally relevant to human exposures, researchers said.